The Silver Case / The 25th Ward
Insanely stylish games. The first chapter is full on psychological horror, the rest is like Serial Experiments Lain: The Game mixed with Film Noir storytelling. 25th Ward is like Texhnolyze mixed with Film Noir storytelling. Both are very abstract and interesting, but because so few people have actually played them, it's hard to find good discussion. The writer (Suda51_ went on to make the more famous killer7 and No More Heroes games.
Aesthetically speaking, they might be the absolute peak of visual novels, maybe even interactive media as a whole:https://www.youtube.com/watch?v=_cfF5JwnnTMhttps://www.youtube.com/watch?v=4PSxkcw_Vr0
(also, there's a game called "Flower, Sun, and Rain" that came out between them that you should play before 25th Ward if you are interested)